Rotary abrading tools of the erasure type are used to remove adhesive material, such as paint and decalcomania, from metal surfaces. The tools frequently include a rotary driven annular disc comprised of an elastomeric material, called an “eraser wheel.” The eraser wheel is rotated at high speeds and pressed against adhesive material for removal. Eraser wheels of this type tend to become deformed over time and, consequently, lose their efficacy. Furthermore, pressing the circumferential surface of the rotating wheel to a target surface generates a significant amount of frictional heat. The heat may cause damage to the wheel and may cause the residue of the abraded adhesive material to bond with surface of the wheel.
U.S. Pat. No. 6,309,292 (Montabaur) discloses a rotary abrading tool of the erasure type, an object of which is to correct these problems. The Montabaur eraser wheel is an annular disc comprised of an elastomeric material and includes an outer crown of radially projecting teeth. Montabaur presumes an improved performance over prior eraser wheels based on having bendable, elastic teeth. As stated in the patent, it is further contemplated that the improved performance is due, in part, to a reduction in the required amount of pressure applied by the teeth and to the teeth during operation, when compared to that of prior eraser wheels. Montabaur further asserts that the gaps between the teeth produce an “air effect”, which serves to mitigate the frictional heat generated by the abrading. The Montabaur eraser wheel is secured to a rotary abrading tool by means of a “holder”. The holder comprises a first and second disc-shaped hub, each comprising a central opening, arranged on opposite axial sides of the eraser wheel. Each hub further comprises a plurality of axially directed ribs, which are inserted into axially directed slots defined by an inner annular crown of the eraser wheel. Montabaur shows each rib of the first hub oppositely disposed from, and in contact with, a rib from the second hub. This contact between oppositely disposed ribs presents a problem. When the wheel and holders are tightly secured to an abrading tool, as is necessary for operation, the tips of oppositely disposed members tend to gall and damage each other. The galling is further exacerbated during operation as the wheel is rotating at high speeds, and the assembly is pressed against a surface.
The rotary driven shaft of the rotary abrading tool extends through the central opening of each hub and the central axis of the eraser wheel. An annular chamber surrounding the shaft is defined by the shaft, the holders, and the inner wall of the annular eraser wheel. Montabaur asserts that this arrangement provides an “air cushion effect” when the tool is operating at high rotational speeds, wherein the outer crown of teeth are lifted uniformly from the holder and creates an annular gap between the eraser and disc holder. While Montabaur discloses an eraser wheel that maintains a uniform circular shape during operation, the uniformity is due in large part to the “air cushion effect” that uniformly lifts the outer crown from the holder. When the eraser wheel is applied to a target surface during operation, the annular gap and chamber provide little resistance against the opposing force of the pressure of a target surface against the eraser wheel. This results in the partial collapse of the eraser wheel during operation, and, consequently, the need to apply further pressure in order to compensate for the partial collapse. The lack of stability in the circular form of the rotating eraser wheel adversely affects the efficacy of the tool as the user is forced to determine the optimal applied pressure during operation, which, in turn, adversely affects the life of the wheel. The problem is compounded during operation if the user has to adjust the angle of the tool due to the demands of the target surface and/or adhesive material.
The teeth of the Montabaur eraser wheel have convergent flanks, that is, each tooth tapers toward its outer end. Abrading is effected as an edge of each tooth successively hits the target adhesive material at a high speed, thereby compromising the integrity of the adhesive material. Subsequently, a portion of the material is torn away from the underlying metal surface as the teeth drag across the compromised material. Each radially projecting tooth extends axially on the circumference of the wheel, such that each tooth is axially parallel to the other. During operation, the teeth carry flakes of the abraded adhesive material as they rotate in a circular path. Consequently, the flakes are often thrown off radially from the wheel as it rotates. As such, Montabaur teaches a shield on the rotary abrading tool for the protection of the user from the flakes.
Thus, there is a longfelt need for a rotary abrading tool assembly free from the drawbacks of the earlier tools used for erasure-type abrading. In particular, a tool of this type that provides an eraser wheel assembly that maintains a sturdy circular shape during operation, structures that mitigate damage to the components of the assembly, and includes an eraser wheel that reduces the amount of flakes projected toward the user during operation.